The overall project goal is to elucidate the processes that control the switch between glycolysis and oxidation-phosphorylation modes of ATP generation during the life cycle of Trypanosoma brucei. The studies are focused on the processes that regulate the expression of mitochondrial (mt) genes and that control RNA editing during the life cycle. Experiments are proposed to: (1) Identify and characterize the remaining protein coding sequences, sequences directing editing and regulatory sequences. The nucleotide sequences of (A) uncharacterized maxicircle transcripts that appear to be extensively edited and the remaining 1.9 kb variable region DNA will be determined and analyzed to identify their functions and (B) gRNAs and gRNA genes will be isolated and characterized to assess minicircle coding capacity and provide materials essential to subsequent studies. Alterations in the genetic potential and editing of mutants will be examined, as will RNA processing. (2)Identify and characterize translation products of maxicircle transcripts to assess the physiological consequences of editing. The in vivo translation of edited transcripts in different life cycle stages and the possibility that different proteins may be produced from the same gene depending on editing will be determined. This will assess the physiological consequences of editing. (3)Identify and characterize genes encoding some components of the editosome to determine the precise characteristics of editosome components, their production during the life cycle, the taxonomic distribution of editing and the existence of related but uncharacterized RNA processing mechanisms. (4)Characterize the developmental regulation of editing at the level of gRNA, mRNA, editosomes or other factors in order to identify and characterize the regulatory system that controls editing. These studies are intended increase our understanding of basic molecular genetic processes, especially those which are important to the survival of parasites.